Electrical protective system



bmw Asma y lill II iT INVENTORS ELSwa/#WJMEE L. K. vSWART ET AL ELECTRICAL PROTECTIVE SYSTEM Filed Deo. 21, 1955 ATTORNEY Patented Sept. 8, 1936 UNITED STATES PATENT GFFICE ELECTRICAL PROTECTIVE SYSTEM Application December 21, 1935, Serial No. 55,660

11 Claims.

This application is a continuation in part of application, Serial Number 712,640, filed February 23, 1934.

This invention relates to electrical protective systems. More particularly, this invention relates to arrangements for simultaneously grounding a plurality of circuits when induced voltages become impressed thereon. This invention also provides methods and apparatus for preventing a total line outage due to failure of the equipment thereon.

A multiplicity of protector blocks, each having an air gap which breaks down at a predetermined potential, have been used in the telephone art for the protection of each of a number of telephone circuits from high voltages set up therein by one or more sources extraneous to the circuits themselves, A multiplicity of relays, a single contact on each of which is associated with a single protector block, are used to short-circuit the various protector blocks so as to prevent a permanent closing of the gap or space within each of the various protector blocks and thereby vastly increase the life of each protector block before it becomes permanently grounded. Without such apparatus, the circuit or circuits to which the protector blocks are connected may be rendered inoperative until the protector block or blocks, which have been grounded, have been repaired or replaced.

In the short-circuiting relay protector apparatus as now manufactured, there is a possibility of permanently grounding the telephone lines to which this apparatus is applied upon the occurrence of a defect in one of the pilot relays employed in this apparatus. This grounding of the telephone wires can be brought about by any circumstance that may cause, for example, the alternating current relay (to be subsequently described) to remain operated for a long, abnormal period of time. Such circumstances may arise on account of improper adjustments in the alternating current relay or of other relays of the apparatus, or improper manufacturing construction of these relays, or upon the occurrence of abnormal temperature changes, especially if the relay contacts are initially set at too critical an adjustment. Additional circumstances for improper operation may be brought about also by undue haste or carelessness in replacing the covers upon the various relays of the apparatus.

This invention will be better understood from the detailed description hereinafter following, when read in connection with the accompanying drawing. Figure 1 of which shows embodiment of the invention merely for the purpose of illustration, Fig. 2 is an illustration of part of the apparatus of Fig. l, and Fig. 3 illustrates a modification of a (different) part of the apparatus of Fig 1.

In the drawing, reference characters W1 to We, inclusive, represent wires of an open wire line or conductors enclosed within a cable to which protector blocks P1 to P0, inclusive, are respectively connected, each in series with the primary winding L1 of a saturating transformer T. The shortcircuiting relays of the arrangement are designated by the reference characters R10, R20 and R30, and their windings are connected in parallel relationship with each other, although it will be understood that these windings may equally well be connected in series relationship. The contacts of the relay R10 function to short-circuit the protector blocks P1 and P2. The contacts of the short-circuiting relay R20 shirt-circuit the protector blocks P3 and P4 and the contacts of the short-circuiting relay R30 short-circuit the protector blocks P5 and P6.

The operation of the short-circuitng relays R10, R20 and R30 is brought about by the closure of the contact of a master alternating current relay designated R0, the winding of which is connected to the secondary winding L2 of the saturating transformer T through a condenser C. The closure of the contact of the alternating current relay R0 applies a local battery B to the windings of all of the short-circuiting relays R10, R20 and Rao, the windings of these relays being connected to the battery B through the armature l5 and the back contact i4 of the relay R1. Thus the short-circuting relays R10, R20 and R30 may be operated by current from the battery B only when the armature i 5 of the relay R1 closes the contact le?, but when contact ill is open, these relays fall off. It will be understood, however, that the contacts of the relay R0 may, if desired, be substituted for the equivalent contacts of any pilot relay of the copper oxide type of relay protector apparatus familiar to those skilled in the art.

The relay R1 is composed of two windings designated 2 and 3, and it includes two armatures designated 8 and i5. The winding 2 controls the attraction of the armatures 8 and. I5. The winding 3 controls the release of these armatures 8 and I5. When no current flows through the winding 2 after the armatures 8 and l5 have been attracted, the armatures 8 and l5 will remain locked up mechanically until later released by the flow of current through the winding 3 of the relay.

Thus when current flows through winding 2 from source B over the circuit which includes the armature 4 and contact 5 of the thermal relay TH, the armatures 8 and I5 will both be attracted. The armature I5 will then leave contact I4 and the armature 8 will close the contact l. Both armatures will remain mechanically locked up in these positions until later released by the action of winding 3 of the relay R1. When the armature of the thermal relay TH leaves its contact 5 the armatures 8 and I5 will, however, remain in their former locked positions. When current later ows from battery B through the winding 3 of the relay R1 over the circuit which includes the armature 4 and the contact 6 of the thermal rel-ay TH and over the armature 8 and contact I of the relay R1, then the energization of this winding will bring about the release oi the armatures 8 and I5.

The releasing action of the winding 3 of the relay R1 is under the control of the armature II of the device SE or of the key K provided armature 4 is in contact with contact S of relay TH. If the armature I I is grounded by any of its various Vcontacts except contact I2, the winding 3 of the relay R1 may then release armatures 8 and I5 provided armature 4 is still in contact with contact 5 of the relay TH. When the armature II is ungrounded as at contact I2, the key K may be operated so as to ground the winding 3 of the relay R1 through winding IU of the selector. VAt the same time that Winding 3 of the relay R1 is operated, winding I of the selector operates to restore arm II of the selector to the normal unoperated position, in a manner well understood by those skilled in the art.

The relayR0 is operated by the potential applied through the condenser Cv from the secondary winding L2 of the saturating transformer T. The potential set up in the transformer T is derived from the current flowing to ground throughY the primary winding L1 from any one or all of the several protector blocks P1 to Ps when the potential applied across any of 1 these protector blocks exceeds the break-down value. At the same time that the potential of battery B is applied simultaneously to the windings of all the short-circuiting relays R10, R20 and R30, the potential of battery B is also applied to the Winding of the thermal relay TH, the circuit to the winding of this relay being completed through the armature I and the back contact I4 of the relay R1 and through the armature and contact of relay R0. If this potential is applied longer than a specied, predetermined interval of time, the thermal rel-ay TH will become operated. This will cause its armature 4 to leave its contact Ei Vand then close with contact 5. Upon the closure of the contact 5, current will ow from the battery B through the armature 4 and the contact 5 of the thermal relay VTH and through the winding 2 of the relay R1 and ground. A ow of current through the winding 2 of the relay R1, will cause its armature 8 to close contact 'I and at the same time cause its armature I5 to leave its back contact I4. The opening of the back contact I4 will instantly break the circuit which transmits current from battery B through the windings or" all of theshort-Vcircuiting relays R10, R20 and R30, permitting the latter relays to fall off temporarily. It will be noted by reference to Fig. 2 that by the energization of Winding 2 of the relay R1, the contact 'I and armature 8 are mechanically held closed and at the same time the contact I4 is mechanically held open from Varmature I5. Thereafter armatures I5 and 8 of relay R1 are under the control of winding 3 of relay R1.

In addition to operating relay R1, the closure of the contact 5 by the armature 4 ofthe thermal relay TH, as described above, will cause current to flow from the battery B through the armature 4 and the contact 5 of the relay TH, and through the stepping magnet 9 of the selector SH. This will cause rotation of the armature II of the selector SE in a clockwise direction until it reaches the rst contact of the selector. At'the same time the opening of the back Contact I4 will stop the ow of current from the battery B through theY winding of the thermal relay TH, thereby permittingY the thermal relay TH to cool to a lower temperature.

VWhen the thermal relay has become sufficiently cooled, itsarmature 4 will leave contact 5 and restore to contact 5. Current will Yagain ilo-w from the battery B through the armature 4 and the contact 6 of the thermal relay TH, and through the armature 8 and the contact 'I and the Winding 3 of the relay R1, and through the armature II and the rst contact of the selector SE through ground. This will cause the magnet 3 of the relay R1 to release its armatures 8 and I5, which have been mechanically heldin the operated position following the operation of magnet 2 of relay R1. When the armature I5 again closes the back Contact I4 of the relay-R1, the battery B again supplies current to the windings of all of the short-circuiting relays R10, R20 and R30, and current again flows from the battery B through the winding of the Vthermal relay TH, both circuits just described being completed through the armature I5 Vand theback contact operation above described will be repeated again V and again. It willV be evident that after the winding of the thermal relay becomes sui'liciently heated, the armature 4 will leave contact 6 and close its contact 5 and allow current to ow from the battery Brover contact 5 to the winding of the stepping magnet 9 so that the armature II will be rotated in a clockwise direction to the second contact of the selector SE and at the same time supply currentfrom the battery B through the winding 2 of the relay R1 over the same contact 5 of the thermal relay TH. The armatures 8 and I5 will again be attracted, the armature 8 closing contact 'l and the armature I5 opening the contact I4 of the relay R1. Winding 3 of the relay R1 will be grounded through the arm II of the selector S11 and will remain unoperated. But just as soon as the thermal relay THV again cools to a suiciently low temperature, the armature 4 of this relay will again leave the Ycontact 5 and then close its contact 5, again causing current to flow from the battery B through the winding 3 of the relay R1, over a circuit which includes the armature 8 and the contact 'I of the relay R1. This willV again release the armatures 8 and I5 and again allow current to flow from battery B over the circuit of armature I5 and the back contact I4 of the relay R1 to the windings of all of the short-circuiting relays R10, R20 and R30.

II for any reason the relay R0, or the correspending pilot relay in other arrangements, remains operated when the arm I I of the selector SE reaches its last contact designated I2, the arm II will then become ungrounded and the magnet 3 of relay R1 will no longer be able to receive current from the battery B. Thus, the relay R1 will remain mechanically locked up. It will be apparent that while the relay R1 remains locked up, the opening of the back contact I4 of relay R1 will prevent the short-circuiting relays R10, R20 and R30 from becoming operated and at the same time prevent the winding of the thermal relay from receiving current from the battery B. The attention of an attendant will then be required to restore the circuit to its normal condition.

The arm II of the selector SE is shown connected in series with a key K and the winding of a magnet II) and ground. This key K may be located at the protector apparatus or it may be located at a remote point, as for example, the switchboard of a repeater station, or, if desired, two or more keys may be paralleled to each other, one being located at the protector apparatus and the other at a remote point, if found necessary. The closure of the key K will ground the winding of the magnet 3 of the relay R1 through the winding i9 of the selector SE, independently of the arm II of this selector, so that current may flow through the winding 3 of the relay R1 from the battery B, over the armature 4 and contact 5 of the relay TH, and over the armature 8 and the contact 'i of the relay R1. It will be apparent, of course, that the flow of current from the battery B through the winding 3 of the relay R1 will simultaneously release both armatures 8 and i5 of this relay so as to again allow current to flow from the battery B through the winding of the thermal relay T11 as well as through the windings of all the short-circuiting relays R10, Ran and R30. If the condition of trouble has not been cleared the procedure of operation as just described will be repeated until the selector arm Il steps around to the last contact l2. Hence key K should be operated only to indicate a permanent trouble or to restore the apparatus to normal after such a trouble has been cleared. The Winding I 0 of the selector SE is also employed for the purpose of releasing a spring (not shown) so as to allow the arm II of the selector SE to be returned from its last contact I2 to its initial position.

In Fig. 3 is shown an arrangement by which it is possible to restore the apparatus to normal when arm il is on any contact in the course of its travel. The selector SE is equipped with offnorrnal contacts I6 and I'I which at any point in the motion of the arm II other than the normal uncperated position will close contact I6 with arm i'! and place winding I@ of the selector under the control of key K without the circuit being completed through winding 3 of the relay R1 as shown in Fig. 1. When the arm II of the selector is in its unoperated position, arm I'I of the off-normal contact remains in contact with contact I3. With arm II on any contact point in the course of its travel, the battery circuit B for winding il! of the selector is completed through arm i and contact 6 of the thermal relay TH, through winding II) and the selector arm il and contact 6 of the oli-normal contacts of the selector SE and the key K to ground. Thus,- when key K is pressed, the winding I0 will operate to restore arm II of the selector to its norunoperated position.

After the arm I I of the selector SE has reached its last contact I2 and the key K of Fig. 1 is unoperated, the protector blocks P1 to Pe will remain unprotected, and, of course, those blocks may become grounded due to the presence of extraneous high voltages upon their associated conductors. It is improbable, however, that all of the conductors W1 to We, or, if more than six conductors are employed, that a large portion of them will continue to receive extraneous high voltages for the reason that a surge of voltage originating from, for example, a power line, is generally unable to outlive the sequence of events which bring about the intermittent operation of the thermal relay T11 and the stepping apparatus of the selector SE. The existence of such a prolonged application of extraneous high voltage probably would iirst seriously damage the power equipment itself, and if the power circuit itself becomes damaged, it may then become impossible for the extraneous voltage to be applied to any one of the exposed conductors W1 to Ws.

The thermal relay TH may, for example, cornprise a pair of metallic strips having diierent coeicients of thermal expansion which are tied, riveted or welded together. One of these strips, for example, the one having the higher coefficient of thermal expansion, may be shorter under normal temperature conditions than the strip having the lower coefficient of thermal expansion. These strips may together form a flexible armature, and under normal conditions of temperature, be so bent as to cause the closure of contact B of the thermal relay TH. The winding of the relay TH may include a plurality of turns of resistance wire and this winding may be positioned about either of the metallic strips or about both of the strips, or it may be placed in a position not far distant from either or both of these strips so that when current iiows through this winding, one or both of these strips will be heated to substantially the same temperature. In such an arrangement the application of a high temperature will cause the strip having the higher temperature coefficient to become longer than the one of lower temperature coefficient. Then the armature will be deflected in the opposite direction so as to close the contact 5.

While this invention has been shown and described in a certain particular arrangement merely for the purpose of illustration, it will be understood that the general principles of this invention may be applied to other and widely varied organizations, without departing from the spirit or the invention and the scope of the appended claims.

What is claimed is:

l. The combination of a plurality of conductors which are exposed to interference, a plurality of protector blocks which are respectively connected to said conductors, a plurality of shortcircuiting relays having their windings connected in parallel relationship and having their armature contacts arranged so as to bridge said protector blocks, an alternating current relay which becomes operated when a suiciently high potential becomes impressed across any one or all of said protector blocks, a source of potential, a thermal relay, and a relay arrangement controlled by said thermal relay, said relay arrangement having an armature and contact which are connected in series with said source of potential and the windings of all of said shortcircuiting relays upon the operation of said alternating current relay, the armature and contact of Vsaid relay arrangement being also connected in series with said source of potential and the Winding of the thermal relay, the operation of said relay arrangement occurring at intervals corresponding to the Yintervals required for the operation of the thermal relay.

. In-apparatus for the protection of a plurality of circuits exposed to interference, the combination of a source of potential, a thermal relay, a 'relay apparatus including aV magnetizingwinpling which controls an armature and a Contact, and a plurality of short-circuiting relays, said source of potential being connected in series Vwith the winding of the thermal relay through the armature and contact controlled by the magnetizing Winding of the relay apparatus, said source of potential being also connected to the windings of all of said short-circuiting relays through the armature and contact controlled by the magnetizing Winding of the relay apparatus. The combination of a plurality of conductors which are exposed to interference, a plurality of protector blocks associated with said conductors, a saturating transformer or reactor connected to said conductors through the various protector blocks, an alternating current relay, a plurality'o short-circuiting relays the armatures and contacts of which simultaneously short-circuit all of said protector blocks when said relaysV become operated, a source of potential, a thermal relay, and relay apparatus including a magnetizing Winding and an armature and contact under the control of said inagnetizing Winding, said source of potential being connected in series with the armature and contact or" the alternating current relay and the windings of the short-circuiting relays through the armature and contact controlledV by the magnetizing Winding, said source of potential being also connected to the winding of the thermal relay through said armature and Contact controlled by said magnetizing winding.

4. The combination of a plurality of conductors, means for simultaneously grounding all of said conductors upon the application of an abnormal potential to any one of said conductors, a thermal relay for interrupting said grounding means, and step-by-step apparatus for releasing and operating said thermal relay a predetermined number or" times.

5. The combination of a current-carrying circuit exposed to interference, means for grounding' said circuit upon the application to said circuit of a voltage exceeding a predetermined value, a thermal relay, means controlled by said thermal relay for interrupting said grounding means, and

step-by-step apparatus responsive to the operation of said thermal relay for releasing said thermal relay and repeating its operation a predetermined number or" times.VV

6. The combination of a plurality of currentcarrying circuits exposed to interference, means for simultaneously grounding all of said circuits upon the application to any one of said circuits of voltageV exceeding a predetermined value, a thermal relay, means controlled by said thermal relay for interrupting said grounding means, and step-by-step apparatus responsive'to the operation of saidthermal relay to periodically release said thermal relay and repeat its operation until the induced Voltage is reduced below said predetermined value.

7. The combination of a plurality of exposed conductors, an alternating current relay, means responsive to the application of an excessive voltage on any one of the exposed conductors for operating the alternating current relay, means responsive to the operation of the alternating current relay to simultaneously ground all of the exposed conductors, and thermal means coupled to the alternating current relay, said thermal means including means for periodically opening the grounding circuit for the Various exposed conductors after the alternating current relay has operated.

8. The combination of a main circuit, an alternating current relay controlled by Vsaid main circula-a thermal relay connected to the alternating current relay, means responsive to the operation of the alternating current relay to vibrate the armature of the thermal relay, said armature being coupled to the main circuit.

9. In a circuit for grounding an exposedconductcr, the combination of a thermal relay and means responsive to the operation of the thermal relay to periodically break the grounding circuit.

10. The combination of an exposed line, a mainV relay connecting the line to ground upon the impression of an extraneous voltage, a thermal relay controlled by the main relay, and means controlled by the thermal relay to periodically open and close the ground connection established to said line.

1l. The combination of a relay, thermal means responsive to the operation of said relay to periodicaliy operate and release said thermal means, a plurality ofY circuits, and means responsive to each operation of said thermal means to simultaneously ground all of said circuits.

' LELAND KASSON SWART.

JULIAN BRENNER TEBO. 

